linux-kernel - Re: [PATCH] x86, kaslr: avoid setup

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Date:	Wed, 01 Oct 2014 11:13:55 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Kees Cook <keescook@...omium.org>
CC:	LKML <linux-kernel@...r.kernel.org>, Baoquan He <bhe@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Wei Yongjun <yongjun_wei@...ndmicro.com.cn>,
	Pavel Machek <pavel@....cz>
Subject: Re: [PATCH] x86, kaslr: avoid setup_data when picking location

On 10/01/2014 11:08 AM, Kees Cook wrote:
>>
>> The use of (u64) in the assignment to avoid.start gives a nuisance
>> warning on 32 bits.
> 
> Ah, good catch! This should be (unsigned long), I think. Shall I send
> a follow-up patch, or do you want to fix this directly?
> 

Please do.

In theory it is possible for a bootloader to put an object above 4G even
for a 32-bit kernel, but that is likely to break any kind of other
things, so I'm not worried about it.  You don't need to worry about
avoiding such a zone, the problem is mostly that you can't follow the
list any further without adding PAE-handling code.

	-hpa


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